Duchenne and Becker Muscular Dystrophy (DBMD) are progressive muscle wasting diseases caused by a mutation in the gene that codes for the muscle protein, dystrophin. The incidence of DBMD is commonly given as 1/3500 (0.29 per 1,000) male births and is considered the most common lethal pediatric disorder worldwide. Recent studies of prevalence of DMD and BMD in the United States are lacking. The primary objectives of our long-term surveillance project are: 1) to ascertain cases of Duchenne and Becker Muscular Dystrophy (DBMD) in a defined region of the State to generate population-based data on DBMD;2) to collect information on types of care and care settings for persons with DBMD and evaluate whether care received influences severity or course of DBMD and/or whether it satisfies family needs based on family reports and quality of life measures;3) to collect information on early signs and symptoms as well as types and prevalence of complications;4) to conduct additional DNA tests and evaluate whether the severity or course of DBMD can be predicted by the type of mutation (e.g., genotype-phenotype correlation);and 5) to assess whether race, ethnicity, socioeconomic status (SES) or other demographic variables correlate with types of care patients and families receive. Common protocols and tools will be used that were developed by the Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet) during the past three years. These include a case definition and surveillance protocols along with software applications for medical record abstraction, clinical review and pooled data. Neuromuscular specialists at each of the five participating sites (Arizona, Colorado, Georgia, Iowa and New York) will continue to review pooled data to determine if a case meets case criteria. A multiple source ascertainment methodology has been most efficient and will continue to be used to identify individuals with DBMD. The following types of sources have been used: neuromuscular specialty clinics and diagnostic facilities, the hospital discharge database, community pediatricians and developmental specialists, and death certificates. MD surveillance differs from traditional birth defects surveillance as children will be diagnosed at an older age and usually not hospitalized at the time of diagnosis. RELEVANCE: Determination of the U.S. prevalence of DBMD both currently and over time will help us understand (1) the burden of disease on society and (2) if and how various factors such as genetic counseling and changes in management/treatment of DBMD, particularly prednisone therapy, are influencing prevalence and long-term outcome. The mechanisms and risk factors for these mutations are not well understood, and this study may increase our knowledge here through planned examinations of various demographic and lifestyle exposures, both occupational and environmental.